.diamond {
  height: 0;
  width: 100px;
  position: relative;
  border-bottom: 30px solid skyblue;
  border-left: 15px solid transparent;
  border-right: 15px solid transparent;
}

.diamond:after {
  position: absolute;
  border-top: 70px solid skyblue;
  border-left: 50px solid transparent;
  border-right: 50px solid transparent;
  top: 30px;
  left: -15px;
  content: '';
}
